Re: Digital Pyrometers

[Hank Murrow]

On Nov 10, 2009, at 2:49 AM, gary navarre wrote:

> Hay Gang,
>
> Those old analog pyrometers of mine need something... the
> thermocouples with no protective ceramic covering have a couple
> ceramic flex joint spacers missing and the needle adjustment screw
> on one turns all the way round and sort of finds room temperature.
> I cleaned the contacts and I am getting a rise and fall reading but
> they're far from accurate. So I can decide what I need could
> someone explain the difference between an S Type and a Type K
> thermocouple?

Gary, the type K is a chrome/alumel alloy, while the type S is
platinum/rhodium. this explains the difference in cost, the first
going for $15_$20, the type S around $200. The chrome/alumel ones are
not useful(accurate) past cone 5, while the type S are good to well
above cone 13.
>
> Also, I've thought of recording the heat rise and fall in my wood
> kiln kinda like those old machine maintenance circle graphs but
> wished there was a way to hook it up to a computer and look what
> they have... a computer interface system. So, I have an old
> computer I don't use on line anymore with Windows 98 and enough
> space... would the idea be to save any data I want to keep to an
> external hard drive and reformat it to clean it up before
> installing this software. Then I could build a safe spot by the
> kiln to accommodate the computer for recording the week or so of
> firing. There would be no need to use the electric kiln controller
> stuff but it would be there if I ever got a small test kiln. I'm
> thinking I could also hook up the JVC and video stoking activities
> for 10 hours at a time and have a time stamp that will match the
> electronic graph. Is that what this system will do or is there
> something simpler... like a pad of paper, take notes by hand, and
> state the data for the camera? I'll probably do that too but the
> thing is I plan to leave the kiln firing itself unattended for
> quite a while in the beginning and middle of the fire so it would
> be a cool way to get kiln data.

R4ecently this year on Clayart, someone mentioned a sweet little
interface to do just that that went for around $100. I tried to find
the link but failed this morning.

Cheers, Hank
>
>
> Gary Navarre
> Navarre Pottery
> Navarre Enterprises
> Norway, Michigan, USA
> http://www.youtube.com/GindaUP
> http://public.fotki.com/GindaUP/
>
>
> --- On Sun, 11/8/09, Scott Harrison <shar...@HUMBOLDT.K12.CA.US>
> wrote:
>
>> From: Scott Harrison <shar...@HUMBOLDT.K12.CA.US>
>> Subject: [Clayart] Digital Pyrometers
>> To: Cla...@LSV.CERAMICS.ORG
>> Date: Sunday, November 8, 2009, 9:34 PM
>> Thank you for all your responses. I
>> saw several Fluke 52's on Ebay but
>> also found that Skutt has a new model out for $110.00 that
>> will work
>> pretty well for my purposes and my school budget. http://
>> www.skutt.com/products/accs.html
>>
>> Scott Harrison
>> South Fork High School
>> Humboldt Redwoods CA
>>

[rickma...@comcast.net]

Gary,

 

Why not position the pyrometer where the JVC can see it so it is all on the video?

I know that would be cumbersome when it came to getting the data but it would be the low tech situation.
All pyrometers are actually voltmeters with a face that reads in degrees (or lcd screen that reads in degrees) you need to look up how to take voltmeter readings in micro-volts and have them recorded by your computer.  That said it is important to pull maintenance on your thermocouple connections if you want any consistency over time.  The contacts become dirty or corroded and the reading suffers (on the low side).

 

YMMV,

Rick

 

 

--
Photo log at:  http://claycraft.blogspot.com/
To unsubscribe send email to Claycraft-...@googlegroups.com

[Irakusa]

Does anyone else have to flick the screen of their pyrometers to get the needle to move, sort of like in movies of WWII pilots tapping the guages?

---

From: "rickma...@comcast.net" <rickma...@comcast.net>
To: clay...@googlegroups.com
Sent: Tue, November 10, 2009 10:03:35 AM
Subject: Re: *ClayCraft* Re: Digital Pyrometers

[Sherron & Jim Bowen]

Yes, and that's why I got rid of the old analog type thermometer.  You can buy Omega and Fluke digital thermometers on eBay for less than an analog one. Then you just need to get  a plug for the digital and hook up your old thermocouple and be good to go.

JB

[rickma...@comcast.net]

I do, sometimes that helps when the pyrormeter is cold.

[rickma...@comcast.net]

I have a really good expensive analog pyrometer that I bought in Japan and it moves quite easily, no need for tapping, it really is an instrument.  It is also abo ut 3" 5 x 6.5" X 10" with a nice leather handle.

[Hank Murrow]

On Nov 10, 2009, at 2:49 AM, gary navarre wrote:

> I've thought of recording the heat rise and fall in my wood kiln
> kinda like those old machine maintenance circle graphs but wished
> there was a way to hook it up to a computer and look what they
> have... a computer interface system. So, I have an old computer I
> don't use on line anymore with Windows 98 and enough space... would
> the idea be to save any data I want to keep to an external hard
> drive and reformat it to clean it up before installing this
> software. Then I could build a safe spot by the kiln to accommodate
> the computer for recording the week or so of firing. There would be
> no need to use the electric kiln controller stuff but it would be
> there if I ever got a small test kiln. I'm thinking I could also
> hook up the JVC and video stoking activities for 10 hours at a time
> and have a time stamp that will match the electronic graph. Is that
> what this system will do or is there something simpler... like a
> pad of paper, take notes by hand, and
> state the data for the camera? I'll probably do that too but the
> thing is I plan to leave the kiln firing itself unattended for
> quite a while in the beginning and middle of the fire so it would
> be a cool way to get kiln data.

R4ecently this year on Clayart, someone mentioned a sweet little
interface to do just that that went for around $100. I tried to find
the link but failed this morning.

I found the link and here it is: http://www.picotech.com/data.html

Cheers, Hank

[Louis Katz]

These meters run on very small forces. Its not so much the millivolts that are the problem but the very small amperage. Unless the meter is very well made the friction or lack thereof in the pivot is critical. Good quality meters cost, but can last near forever with good care. I believe the one in the Bray kiln room used by Volkous is still in use.

Type R or other noble metal Thermocouples are much superior and worth the cost under most circumstances, but you need a protection tube. It is probably worth ordering stuff from Omega Engineering. You might find an "exotic" protection tube that will hold up better than the normal ones. Make sure your meter is made for the type of thermocouple you are using.

Using a good meter is necessary if you are planning to use the readings in any sort of absolute manner.. The temperature of the meter, and the connections at the meter all make a difference and you need something temperature compensated somehow.

Also you need the correct lead wires. They are different for different thermocouples.

Skutt Kiln control boards (same as some other manufacterers use) have a communications port that can be hooked up to a computer. I have not done this.

There was an article in one of the mags years ago about using a computer to control your kiln. I built a controller to do this with my radio shack color computer II. I used an Analog Devices temperature measurement chip for most of the work. I tested the thing but never used it.. By the time I got it built I was done with slipcast glass.

Now I would go to the Omega Engineering site and call one of their reps. There are lots of standalone boards, and controllers that interface with PC's. I look I drool. I use cones .

Anyone out there in clayerville play with Arduino boards?

Louis

--- On Tue, 11/10/09, rickma...@comcast.net <rickma...@comcast.net> wrote:

> From: rickma...@comcast.net <rickma...@comcast.net>
> Subject: Re: *ClayCraft* Re: Digital Pyrometers
> To: clay...@googlegroups.com
> Date: Tuesday, November 10, 2009, 2:19 PM
> #yiv1949050115 p
> {margin:0;}I
> have a really good expensive analog pyrometer that I bought
> in Japan and it moves quite easily, no need for tapping, it
> really is an instrument.  It is also abo ut 3" 5 x
> 6.5" X 10" with a nice leather handle.
>  
> Rick
> ----- Original Message -----
> From: "Sherron & Jim Bowen"
> <jbow...@prairienetworks.com>
> To: clay...@googlegroups.com
> Sent: Tuesday, November 10, 2009 9:41:30 AM GMT -08:00
> US/Canada Pacific
> Subject: Re: *ClayCraft* Re: Digital Pyrometers
>
>

> #yiv1949050115 DIV {
> MARGIN:0px;}

>
>
> Yes, and that's why I got rid
> of the old analog type thermometer.  You can buy Omega
> and Fluke digital thermometers on eBay for less than an
> analog one. Then you just need to get  a plug for the
> digital and hook up your old thermocouple and be good to
> go.
> JB
>
> ----- Original Message -----
>
> From: Irakusa
> To: clay...@googlegroups.com
>
> Sent: Tuesday,
> November 10, 2009 10:32 AM
> Subject: Re:
> *ClayCraft* Re: Digital Pyrometers
>
>
>
> Does anyone else have to flick the screen of their
> pyrometers to get the needle to move, sort of like in movies
> of WWII pilots tapping the guages?
>
>
>
>
>
>

> From:
> "rickma...@comcast.net"
> <rickma...@comcast.net>
> To: clay...@googlegroups.com
> Sent: Tue,
> November 10, 2009 10:03:35 AM
> Subject: Re:
> *ClayCraft* Re: Digital Pyrometers
>
>

> #yiv1949050115 p {margin:0;}

[Mike]

Here in Japan everyone seems to use/sell type R, and they're 5-7 hundred dollars each, depending on length. I have 12" type K, but they're too short for use in the wood kiln that I'll be firing. Are there any type K longer than 12"? I don't really care about accurate temp readings at high temps, since I pull test pieces as I fire. I'm more concerned with knowing when the temp is climbing and falling. Plus, I already have a fluke pyrometer that takes the K type.

Thanks,

Mike

Mike
in Taku, Japan

karatsupots.com
karatsupots.blogspot.com
karatsupots-workshop.blogspot.com/

Hank Murrow さんは書きました:

[Paul Herman]

Hi Mike,

I use type K probes in two places in our kiln here. They are the 12"
variety and I get them from Laguna Clay. Last time I bought some a few
years ago, they were $12 apiece, and I figured it would take longer
than my life expectancy to justify getting a platinum S type probe,
not to mention a new pyrometer (I have an Omega.) So these are kind of
heavy wire and there is a porcelain protective tube for them. They
last about eight or so firings in the anagama chamber, because of the
extended firings I think. In the upper chamber the first one is still
good after 20 firings. Like you, we are not interested in accuracy so
much as whether the temp is climbing or falling. I only have one new K
probe on the shelf, so I guess it's time to buy 3-4 more. I have seen
18" ones, but not in the Laguna catalog.

I wish I could come to your kiln building workshop. What is the shape
of the planned kiln?

Best wishes,

Paul Herman

Great Basin Pottery
Doyle, California US
www.greatbasinpottery.com/

[Lee]

On Wed, Nov 11, 2009 at 3:43 PM, Mike <mi...@karatsupots.com> wrote:
> Here in Japan everyone seems to use/sell type R, and they're 5-7 hundred
> dollars each, depending on length. I have 12" type K, but they're too short
> for use in the wood kiln that I'll be firing.

Mike, can you make a recess in the wall and insulate it with fiber so
that a 12" will work? Those are gonna be mighty thick walls.

--
Lee Love in Minneapolis
http://mingeisota.blogspot.com/
"The intuitive mind is a sacred gift and the rational mind is a
faithful servant. We have created a society that honors the servant
and has forgotten the gift." -- Albert Einstein

[Des & Jan Howard]

Mike
Briefly.
Types S, R & T are platinum/platinum-rhodium
thermocouples. Type R is the usual platinum
thermocouple in Oz. Expensive, mine are in ceramic
sheaths, mostly as an anti-trauma effort.
Type N is a Nisil/Nicrosil thermocouple, useful to
1300oC, but I only use it in my electric low-fire kiln,
the kiln controller uses Type N.
Type K is a chromel/alumel thermocouple, cheap as
chips, theoretically useful to 1370oC, but unsupported
sag at about 1220oC, ceramic sheaths would be a good
idea, buy compensating leads for Type K & hook it up
to your Fluke.
Des

Mike wrote:
> Here in Japan everyone seems to use/sell type R, and they're 5-7 hundred
> dollars each, depending on length. I have 12" type K, but they're too
> short for use in the wood kiln that I'll be firing. Are there any type K
> longer than 12"? I don't really care about accurate temp readings at
> high temps, since I pull test pieces as I fire. I'm more concerned with
> knowing when the temp is climbing and falling. Plus, I already have a
> fluke pyrometer that takes the K type.

--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850

02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624

[Mike]

Thanks Paul,

Having the thermocouples poop out after 8 or so firings was something I hadn't thought of.  I found a place that has the R type for about $400 in the length I need. So the question is, one of the R's or 12 - 15 of the K's, I suppose.

Anyway, life expectancy is definitely something to consider. I wonder how the R's and S's do in extended firings?

The kiln for the workshop is a caternary arch anagama with an additional caternary chamber added between the main chamber and the chimney.

http://karatsupots-workshop.blogspot.com/2009/07/kiln-elevation.html

Craig is still working on smaller details, I'm looking forward to seeing what he comes up with.

Mike
in Taku, Japan

karatsupots.com
karatsupots.blogspot.com
karatsupots-workshop.blogspot.com/

Paul Herman さんは書きました:

[Mike]

We're going to put a layer of fiber over the brick, then cover with several inches of  red mountain clay/sand/vermiculite/straw/kitchen sink (haven't worked on the exact formula yet). I didn't think that a probe would project into the chamber far enough . Recessing the area around the probe is a good option.

Mike
in Taku, Japan

karatsupots.com
karatsupots.blogspot.com
karatsupots-workshop.blogspot.com/

Lee さんは書きました:

[Mike]

Hi Des,
What conditions do you use your type R in? Do you have an idea of the life expectancy?

I have R's in my gas kiln, but have no idea how old they are, so don't have an idea of what to expect. If they last well in wood firings, I might consider buying an R for the wood kiln, and toting my Japanese R compatible pyrometer outside when I fire the woody.

Mike
in Taku, Japan

karatsupots.com
karatsupots.blogspot.com
karatsupots-workshop.blogspot.com/

Des & Jan Howard さんは書きました:

[Des & Jan Howard]

Mike
Mention has been made of Pt/Pt-Rh thermocouples
deteriorating in reduction firings. I have only ever
used sheathed Type R's in wood & gas kilns & have never
found a problem.
The exposed Pt wire on my early model OxyProbe, used
only in a gas kiln, did did break eventually, but it
was covered with a layer of glaze/salt.
Des

Mike wrote:
> What conditions do you use your type R in? Do you have an idea of the
> life expectancy?
>
> I have R's in my gas kiln, but have no idea how old they are, so don't
> have an idea of what to expect. If they last well in wood firings, I
> might consider buying an R for the wood kiln, and toting my Japanese R
> compatible pyrometer outside when I fire the woody.

[Lee]

On Thu, Nov 12, 2009 at 2:43 AM, Mike <mi...@karatsupots.com> wrote:
> We're going to put a layer of fiber over the brick, then cover with several
> inches of  red mountain clay/sand/vermiculite/straw/kitchen sink (haven't
> worked on the exact formula yet). I didn't think that a probe would project
> into the chamber far enough . Recessing the area around the probe is a

Mike, have you considered rice hulls instead of straw?

[Louis Katz]

noble metals can be expected not to oxidize or corrode. However stuff that comes in contact with them can alloy themselves in it or perhaps dissolve is a better word. 

I have no experience in a wood kiln but I would expect to have to change the protection tube, and I would protect the connection block in a recommended housing despite the added cost. I Believe the R in the old softbrick kiln at the bray (reduction) are 50 years old. I will try to remember to check next summer.

[Hank Murrow]

On Nov 12, 2009, at 12:19 AM, Mike wrote:

> Thanks Paul,
>
> Having the thermocouples poop out after 8 or so firings was
> something I hadn't thought of. I found a place that has the R type
> for about $400 in the length I need. So the question is, one of the
> R's or 12 - 15 of the K's, I suppose.

Question I see is "Can you get enough information about temp climb
and fall from one location?" I think you can.

>
> Anyway, life expectancy is definitely something to consider. I
> wonder how the R's and S's do in extended firings?

A type-S is built into my OxyProbe which is set in a 0.5" diameter
Alumina tube, open at the end, the Oxy sensor 0.5" recessed fron the
end. Has gone 300 fires so far.

Cheers, Hank

[Lee]

Des,

I believe all woodfirers use porcelain protection tubes.

[Paul Herman]

Hank,

Though I'm sure one probe will give you enough information to fire the
kiln, it's still nice to have two, one in each chamber. I'm glad we
have it set up that way. After a big stoke, you can see the salt
chamber climbing and the anagama falling. As the flame shortens it
reverses, with the salt chamber falling as the anagama climbs. Then as
the anagama starts to stall it's time to stoke. The one thing that was
trouble at first was we were watching the pyro too much, literally
glued to the tube. Now we have more discipline, and are able to ignore
it, or just check it every hour or two.

Someone mentioned that the tubes won't last forever, and ours have
taken a heavy coat of ash. I suppose they will need replacing
eventually.

Paul Herman

[rickma...@comcast.net]

Mike, have someone coming from the USA bring longer thermocouples and protection tubes, we use thermocouples that are 16 or 18" long with tubes to match.  They go about $25 for the thermocouple and maybe $14 for the tubes.  This is for the cheaper ones not the platinum types.

on the subject of multiple pyrometer/thermocouples :When it comes to data gathering you can never have enough- but that said it is possible to fire without a pyrometer.

 

 

YMMV,

Rick

 

[Hank Murrow]

On Nov 12, 2009, at 8:09 AM, Paul Herman wrote:

> Hank,
>
> Though I'm sure one probe will give you enough information to fire the
> kiln, it's still nice to have two, one in each chamber. I'm glad we
> have it set up that way. After a big stoke, you can see the salt
> chamber climbing and the anagama falling. As the flame shortens it
> reverses, with the salt chamber falling as the anagama climbs. Then as
> the anagama starts to stall it's time to stoke. The one thing that was
> trouble at first was we were watching the pyro too much, literally
> glued to the tube. Now we have more discipline, and are able to ignore
> it, or just check it every hour or two.

Dear Paul;

Every wood kiln I've fired has exhibited that behavior, so I told
Mike that a probe 2/3 of the way back in the roof would be adequate.
I don't know why Type S probes are so expensive in japan, as here
they run around $375_425. anyway, a castable piece in the arch with a
shallow 'pocket' for the probe would allow him to use a 12" one, and
also protect the probe from damage during stacking.

Cheers, Hank

[Mike]

I wanted to thank everyone for all of the great input on thermocouple types. It sounds like the R with a ceramic sleeve will last a good while in a wood kiln. I found a supplier here that has them for about half what everyone else sells them for. No idea why they are cheaper, but I think I'll give them a shot.
My Japanese pyro has 4 zones, with a little extra wire I might even be able to connect everything without moving the pyro from it's place in the gas kiln room.
Also, I think I'll test my remaining K probe in the rear chamber, which won't be at high temps for an extended period. If it does well I can order more.

Rick, who is your source for the longer K probes?
Paul, if you can, we'd love to have you for the workshop next year.

Thanks,
Mike

Mike
in Taku, Japan

karatsupots.com
karatsupots.blogspot.com
karatsupots-workshop.blogspot.com/

Hank Murrow さんは書きました:

[Richard Mahaffey]

Mike, we get those from Clay Art Center, I can check the prices for you or you can check the webiste at:
Clayartcenter.net
The website is not the easiest to use I usually just call to get pricing for orders for school.

Let me know if you want me to check the pricing on the thermocouples and tubes and I will get that info and get it to you as soon as I can.

Rick

[Louis Katz]

Should be able to order them (type K thermocouples) any length you need from Omega.

Last time I looked they sold them in a variety of gauges and lengths with or without the two holed insulators. It was long ago however.

--- On Wed, 11/11/09, Lee <tog...@gmail.com> wrote:

> From: Lee <tog...@gmail.com>
> Subject: Re: *ClayCraft* Re: Digital Pyrometers
> To: clay...@googlegroups.com

[ric swenson]

two dissimilar metals create a small voltage difference... shield them from ambient gases with a ceramic tube.....platinum/platinum rhodium.. so we can read the voltage difference and calibrate to temperature. pyrometers are like magic to the potter. Eye power after 42 years tells me the temperature.. like spitting into the kiln does for the Chinese....


Ric


Jingdezhen Ceramic Institute

--------------------------------------------------
From: "Louis Katz" <loui...@yahoo.com>
Sent: Thursday, November 12, 2009 6:55 AM
To: <clay...@googlegroups.com>

[Des & Jan Howard]

Ric
If your Mark 1 eyeball can tell you if the kiln is
going up, down or stalling, good for you. I use a
pyrometer.
Des

ric swenson wrote:
> Eye power after 42 years tells me the temperature..
> like spitting into the kiln does for the Chinese....

[ric swenson]

yes within half a cone...



ric


I use a pyrometer too. to confirm my eyeballs...hehe

Ric



--------------------------------------------------
From: "Des & Jan Howard" <djho...@hwy.com.au>
Sent: Friday, November 13, 2009 12:28 PM

To: <clay...@googlegroups.com>
Subject: Re: *ClayCraft* Re: Digital Pyrometers

[Des & Jan Howard]

Ric
Good eyeballs :)
Our standard firing requires that the kiln temp be held
from Cone 10 down, Cone 11 just tipped. No more than
+-2 degrees until Cone 11 is well down, about 1 hour.
My eyeballs can't cut it :(
Des

ric swenson wrote:
> yes within half a cone...
> ric
> I use a pyrometer too. to confirm my eyeballs...hehe
> Ric

[ric swenson]

that's a slow slow fire for I hour between cones...

Ha!
going to cone 13 here.


ric

--------------------------------------------------
From: "Des & Jan Howard" <djho...@hwy.com.au>

Sent: Friday, November 13, 2009 1:20 PM

To: <clay...@googlegroups.com>
Subject: Re: *ClayCraft* Re: Digital Pyrometers

[ric swenson]

Jingdezhen now relies on pyrometers and fiber kilns like everywhere else....have not seen an oxyprobe here yet however...except in the ceramic engineering dept.

Ric




--------------------------------------------------
From: "Des & Jan Howard" <djho...@hwy.com.au>

Sent: Friday, November 13, 2009 1:20 PM

To: <clay...@googlegroups.com>
Subject: Re: *ClayCraft* Re: Digital Pyrometers

[Des & Jan Howard]

Ric
Back pressuring the kiln & stalling the temp rise
evens out the kiln, by allowing 'time' to drop
cones not 'temp'.
In our kiln, fast temp rise equals higher flame speed
& causes loss of some of the effects we prefer.
Satins, Juns, celadons & copper reds become glossier
or clear. Microcrystals & colloidal effects disappear.
Des

ric swenson wrote:
> that's a slow slow fire for I hour between cones...

[Mike]

>>Mike, have you considered rice hulls instead of straw?<<

Hi Lee,
Absolutely. Chopped straw just seemed to be on my mind when I wrote the post. I just need to talk to the in-laws soon enough to get the husks and straw. This year I was all set to make my own rice straw ash, and I waited too long to ask my uncle for his crop. When I asked, he said they'd harvested the day before and set the machine to 'puree', so all the straw was chopped short and tossed back on the field. Just try to get that separated from the dirt after you burn it. So I told him I've got dibs on next years crop. He got a good laugh out of it, and promised to set the machine to 'bundle' next year.

You're right, for the kiln insulating coat, the husks will be far easier to use.

Mike
in Taku, Japan

karatsupots.com
karatsupots.blogspot.com
karatsupots-workshop.blogspot.com/

Lee さんは書きました:

On Thu, Nov 12, 2009 at 2:43 AM, Mike <mi...@karatsupots.com> wrote:
  

We're going to put a layer of fiber over the brick, then cover with several
inches of  red mountain clay/sand/vermiculite/straw/kitchen sink (haven't
worked on the exact formula yet). I didn't think that a probe would project
into the chamber far enough . Recessing the area around the probe is a
    

--
 Lee Love in Minneapolis

[Paul Herman]

Mike,

As long as this thread is continuing, I had a few of more thoughts.

The great natural insulation material we use here is diatomaceous
earth, the silica skeletons of little critters that lived in some
ancient sea. I get it as "floor dry" absorbent at the auto supply
store. It's available in the western US, but I doubt so in Japan.
Maybe? Anything that is heat/fire proof and traps a lot of air would
work.

On the pyrometer thing, one more reason to have two probes in a two
chambered kiln is this: After we stop firing the bottom chamber, and
are stoking the salt chamber, we have a pyro to look at for that upper
chamber.

One more thing. If you have one of the high temp thermocouples, that
can take the heat and last, you can put your probe in the hottest part
of the kiln. If you are using a K probe, please put it in a cooler
part of the chamber where it will take less of a beating and last for
more firings.

good stoking and all that,

Paul Herman

Great Basin Pottery
Doyle, California US
www.greatbasinpottery.com/

[teb]

i had a pyrometer for the first few firings of my kiln, but it died
so i fired quite a few times without it and had ok results. the last
(and best) firing, we used one. it was nice to see when it was
reaching 700F so i could pick up the pace a little and nice to see
when it got to 1100F so i could be careful of the refires.
i'd like to use one again for the critical moments, but not for the
entire firing. since i am not broke out in money right now, would it
be a good idea to get a cheaper one and only use it to 1500F or so? i
have some porcelain tubes i got from the corning junkyard in town and
can use them to sheath the thermocouple and hopefully extend it's
life.

[Sherron & Jim Bowen]

Digital thermometer of the type you need routinely bring less that forty
dollars on eBay.

----- Original Message -----
From: "teb" <stink...@gmail.com>
To: <clay...@googlegroups.com>
Sent: Sunday, November 15, 2009 6:20 AM
Subject: Re: *ClayCraft* Re: Digital Pyrometers

[Louis Katz]

Rambling

Whether or not you should buy a thermocouple is a philosophical question.

I suspect that if you should buy one, you should either scavenge the whole thing, build it yourself, or buy something that is good enough to actually work. Depends on how you feel about it.

Me, I am tired of junk. I went looking for a three wing screwdriver (looks like a Phillips head sort of) to take apart some old battery packs and refill them and was expecting to pay 10 bucks or more and get something of good quality. Instead I spent almost 3 dolloars, and we will see about quality, but so far it has worked well.

I like old quality analog meters. Anything that has worked 20 years or more makes me feel good. If the meter was cheap and is twenty years old, it could be as good as it was twenty years ago, but I doubt it. Good meters have the ability to compensate for their own temperatures. They do not give you varied readings until the couple has aged significantly and is very near the end of its life. They are insensitive to changes in amps (determined by the amount of metal at the coupling joint as well as resistance in the wires and connections).Good analog meters have pivots that do not hang, or need tapping.

Similar things are true of good digital meters. A good digital meter should give the same reading when the battery is full and empty, when the meter is at 0 degrees and at 100 F, They should be insensitive to changes in amps when measuring volts. They should last a good long time! They will not last fifty years most likely. Numerous electronic parts have limited lives. Capacitors of the electrolytic kind must be excercised on occasion. I don't know how long different types of displays last, but they seem to have a definite life span.

The other question , whether you should buy one really depends on what kind of potter you are. I think pots, art, artifacts are in many ways imbibed, imprinted, inscribed with thoughts, ideas, and actions of their maker. When someone buys a Hewitt pot, they are buying his whole schtick. I like his work, and think the woodfired potter is timely, meaningful, and relevant. But when you buy his work, there is also the dirt floor, apprentices, natural ingredients, his comments on "The Ice Tea Ceremony" his family history and even his pet pig. You are buying a piece of his life, and even if you do not believe this, you are paying for his life. I like this.

So maybe you should be a potter who gauges temperature by eye. But maybe concern about fuel use, about care, and good quality (whatever that means to you) ware, and about your time take precedence over cost of hardware. I can't tell you.

There are other things. Using a meter can be dulling to your other senses. I teach my students to fire by looking carefully, smelling, and gauging heat rise. The advent of our use of the oxyprobe has not resulted in better (in terms of appearance of fired work) or easier firings here. It has allowed us to use a bit less fuel(this is an improvement)), and seems to have gotten us out of a few rough spots by verifying a change in the way the kiln fires. Pyrometers, are even more useful and perhaps they are the more dulling of the two functions of an oxyprobe. "Oh, temperature is climbing o.k. must not me reducing too hard."

It used to be that I was real sensitive to the difference in color of the edges or tips of things and their bodies. You cand see temperature changes easily this way. Since my reliance on the pyrometer in the reduction kiln my sensitivity seems to be waning.

I think that it appears that the biggest crisis in the world is global warming and the degradation of the environment. I think that perhaps this is only a symptom of our lack of commitment to some kind of quality that would pervade, or be infused in our existence.

Potters in Dankwean Thailand use various gauges. My favorite is a yellow deposit on the chimney rim that tells you it is ok to pick up the pace.

I am in need of good quality grog and am probably going to make it myself.

If you are looking for an inexpensive solution you can use any old voltmeter to tell relative rise and fall. Keep it away from the heat of the kiln and it will work better and last longer.



--- On Sun, 11/15/09, Sherron & Jim Bowen <jbow...@prairienetworks.com> wrote:

[teb]

"Whether or not you should buy a thermocouple is a philosophical question."

that,is the crux of the biscuit!
come what may, i would prefer to rely on myself and not a machine.
thank you for the reminder.
tb